mltframework / mltframework/mlt
avformat: lowres does not work
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- Dominant language
- C
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Description
melt -producer avformat:any_imf_video_file.mxf lowres=3
Expected behavior: output is 1/8 the resolution, 480x270 for a 4K file
Actual behavior: output is full resolution
This is due to AVOptions being set after avcodec_open2() rather than before. This also affects thread_type. Option handling in the avformat module could use improving in general, since there is currently no way to set options for specific streams or to set options only for the demuxer. Getting this right is essential for being able to work with IMF files since they are 4K JPEG2000, which is very CPU intensive without lowres support.
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Research direction
Start in the avformat module and trace how AVOptions are applied around avcodec_open2(). Verify the lowres setting for a 4K IMF video and the thread_type option, then inspect how demuxer- and stream-specific options are represented. Done means lowres produces 480x270 output and the option handling supports the stated use cases.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c
- Domain
- audio-video-rtc
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100